1. Field of the Invention
The present invention relates to a cam-type remote latch mechanism for tightly locking of an enclosed space, like a freezer compartment, a chemical chamber or a drying chamber, particularly to a cam-type remote latch mechanism which is driven by a cam wheel, exerting a sealing force that is adjustable by a screw.
2. Description of Related Art
U.S. Pat. No. 4,880,261 “Remote Latch Mechanism” has disclosed an apparatus for locking a door of an enclosed space, like freezer compartment, a chemical chamber or an oven. As shown in FIG. 8, the apparatus disclosed has a latch assembly with a four-link mechanism, comprising: a housing 91 at a pre-determined position, having a first guiding opening 911 of an elongated shape with a horizontal and an inclined section and a second guiding opening 912; a crank 92, mounted on the housing 91; a link 93, having one end that is hingedly connected with the crank 92; a support 94, having one end that is hingedly connected with the link 93, a first bolt 941 that enters the first guiding opening 911 and a second bolt 942 that enters the second guiding opening 912; and a pawl 95, set on the support 94, defining a right side thereof.
As shown in FIG. 9, in an unlocked state, the crank 92 has a rest angular position, the first and second bolts 941, 942 respectively enter the first and second guiding openings 912 at left ends thereof, and the pawl 95 does not extend outside of the housing 91.
As shown in FIG. 10, the crank 92, when turned away from the rest angular position thereof, drives the link 93 to push the support 94 to the right and thus the first and second bolts 941, 942 away from the left ends of the first and second guiding openings 912 towards right ends thereof, so that the pawl 95 is pushed out of the housing 91.
As shown in FIG. 11, when the second bolt 942 has reached the right end of the opening 912, further turning of the crank 92 has the support 94 follow the path of the first guiding opening 911, resulting in the pawl 95 turning downward after having reached a rightmost position, so that a sealing force is exerted on an external doorframe and, if a sealing strip has been attached to the doorframe, effective sealing is achieved. Turning the crank 92 even further will not result in loosening of the pawl 95 from the doorframe. However, the conventional remote latch mechanism just described has many structural parts and is therefore complicated and expensive to manufacture.
As shown in FIG. 12, the latch 95 has an adjusting device comprising a holding screw 951 screwed into the support 94. The right side of the support 94 and a facing left side of the pawl 95 have sawtooth-shaped surfaces 943, 952. When the holding screw 951 is loosened, the pawl 95 is movable along the right side of the support 94, adjusting the sealing force. With the holding screw 951 tightened, due to friction between the sawtooth-shaped surfaces 943, 952, the pawl 95 has a fixed position with respect to the support 94. However, placing the pawl 95 at a different position with respect to the support 94 requires loosening and retightening of the holding screw 951, which is inconvenient.
As above explanation shows, a conventional remote latch mechanism has several shortcomings.